A Neural Correlate of Predicted and Actual Reward-Value Information in Monkey Pedunculopontine Tegmental and Dorsal Raphe Nucleus during Saccade Tasks
Figure 3
Activity of fixation target neurons of the PPTN for the saccade task. (a, b) A rastergram and peritask event spike density function for the activity of a representative fixation target neuron over 10 successive trials, aligned to the onset of the fixation target. The red and blue rasters (a) and traces (b) indicate large and small reward trials, respectively. In (a), the green squares and circles indicate fixation target onset, the black bars indicate the onset of the saccade target, the black triangles indicate saccade onset, and the green lines indicate the times at which the large (3 bars) and small (1 bar) rewards were delivered. (c) Responses of fixation target neurons to fixation target (squares and circles) presentation (mean response of 200–600 ms after fixation target onset, fixation target/cue period) after reversal of cue-reward contingency. The left panel shows the large-to-small reward reversal, and the right panel shows the small-to-large reward reversal. Large-reward trials are indicated by the dark gray bars, while small-reward trials are indicated by the clear areas. Shown are the mean and standard error of the mean (SEM) of the normalized neuronal activity for the th trial after contingency reversal. The asterisks (*) indicate the activity that was significantly different from the activity during the last 5 trials of the block with the reversed contingency (, Mann-Whitney test). (d) Similar to (c) but for the responses after fixation target offset (working memory period, 200–600 ms after fixation target offset). (e–g) The activity of each fixation responsive neuron is presented as a row of pixels (). (e, f) Changes in the neuronal firing rate from baseline are compared in the large- (e) and small- (f) reward trials. The color of each pixel indicates the ROC value based on the comparison of the firing rate between a control period just before fixation onset (400-ms duration) and a test window centered on the pixel (100-ms duration). Warm colors (ROC > 0.5) indicate increases in the firing rate relative to the control period, whereas cool colors (ROC < 0.5) indicate decreases in the firing rate. (g) Changes in reward-dependent modulation. The ROC value of each pixel was based on the comparison of the firing rate between the large- and small-reward trials. Warm colors (ROC > 0.5) indicate higher firing rates in the large-reward trials than in the small ones. In these 3 panels (e–g), the neurons have been sorted in order of their ROC values for the reward prediction effect during the task period. FTon: fixation target onset; STon: saccade target onset; RWon: reward onset. (Modified from [42].)
